New fatigue limit assessment approach of defective material under fully reversed tension and torsion loading

Abstract

This paper presents a new approach to predict the high cycle fatigue limit of defective material submitted to multiaxial loading. Defects are simplified to a half spherical void at the surface of a specimen. Finite Element (FE) method is used to determine stress distribution around defect for different sizes and loading levels. Papadopoulos high cycle fatigue criterion is used to calculate equivalent stress around defect. Based on stress analysis, a definition of affected area is proposed, in which the Papadopoulos criterion is violated. The evolution of the affected area, versus the amplitude of loading and defect size leads to determine fatigue limit for defective material. Results are in good agreement with experimental investigations and show that the affected area is a good parameter to predict the influence of a defect on multiaxial fatigue behaviour.

Multiaxial fatigue life estimation of defective aluminum alloy considering the microstructural heterogeneities effect

“…Recently, the AA method 33 was proposed to characterize the stress distribution around the defect and to quantify its impact on the fatigue limit under different load conditions. The authors 33 determined the HCF limit of various materials (C35, AlSi7Mg0.3…) based on the AA methodology coupled with the Papadopoulos criterion 35 where Tσ(θ,ϕ) is the generalized shear stress amplitude (MPa) and σH,max is the maximum hydrostatic stress amplitude (MPa).…”

“…The authors 33 defined the AA as the part of the HLP where the considered fatigue criterion is violated (σeq≥β) (Figure 8). In their works, Wannes et al.…”

“…In their works, Wannes et al. 33 conducted an experimental campaign carried out on various defective materials. They followed the change of the AA as a function of the applied load for different defect sizes (area).…”

“…They followed the change of the AA as a function of the applied load for different defect sizes (area). Based on stress analysis and numerical simulations, the authors 33 have showed that for all the defect sizes, when the applied load (σa) is equal to the so-called fatigue limit, the same AA value is obtained. Hence, no matter the defect size, the AA remains constant under the fatigue limit (σD).…”

Prediction of fatigue damage accumulation of defective materials under variable amplitude loading

“…Depending on their size, these imperfections contribute to the degradation of the mechanical properties of the material and they are often at the origin of its failure. [6][7][8][9] Sizing of these components is often done under ideal conditions and in particular for perfect surface conditions.…”